Two interventions (presented individually and in combination) were distributed to staff members via email.
Intervention Start Date
2018-11-21
Intervention End Date
2018-12-21
Primary Outcomes (end points)
Primary outcome: Participation in the organisation’s workplace giving program (where providing any donation counts as 1 and otherwise 0).
Primary Outcomes (explanation)
Secondary Outcomes (end points)
Secondary outcome: Average amount of money per employee directed to workplace giving each fortnight
Secondary Outcomes (explanation)
Experimental Design
A four-arm 2x2 factorial randomised trial. Data (changes in WG) will be tracked for two full pay periods (four weeks) after the intervention delivery.
Experimental Design Details
The trial is a 2x2 factorial design, thus it has two independent variables (IV) each with two levels. IV.A - Messenger
The email were sent from either a member of the DSS senior executive service (SES) or a non-SES staff member (peer). Emails differed only in the name of the sender and their photo.
IV.B - Signup system
Emails included a link to either the current signup information page (current) or a simplified signup form (simplified).
Randomization Method
Randomisation occured in blocks, defined by the following pre-treatment covariates:
• Current workplace giving status (yes/no)
• Income level (below median/above median).
Within each block individuals were randomly assigned to four groups using complete random assignment. Assignment was balanced (that is, an equal number in each treatment group) to the extent that blocks allow.
Randomization Unit
Individual employees.
Was the treatment clustered?
No
Sample size: planned number of clusters
Not applicable.
Sample size: planned number of observations
2,250 staff measured at baseline and two follow-up points (2 and 4 weeks after intervention delivery).
Sample size (or number of clusters) by treatment arms
Participants in the trial will be 2,250 staff. The assignment ratio between experimental groups will be 1:1:1:1
Minimum detectable effect size for main outcomes (accounting for sample design and clustering)
We performed power calculations using simulation for the impact of each of our two interventions. This indicated that at an alpha of 5%, we will have 80% power to detect a standardised effect of 0.11. This is equivalent to a change in workplace giving participation from 1.4% to 3.1%. These calculations assume no interaction effect between the impact of the messenger and the impact of the signup system.
Final Sample Size: Number of Clusters (Unit of Randomization)
number of clusters = 2,436. the unit of randomisation was the individual employee (ie no clustering was used so number of clusters is equal to total sample size).
Was attrition correlated with treatment status?
No
Final Sample Size: Total Number of Observations
n=2,436.
Final Sample Size (or Number of Clusters) by Treatment Arms